Tanning of fur skins



Patented Feb. 16, 1932 UNITED STATES PATENT] OFFICE AIiLEN ROGERS, 0FBROOKLYN, NEW YORK, ASSIGNOR TO THE ROESSLER & HASSLACHEB CHEMICALCOMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE TAN HING- OI' FURSKINS No Drawing.

This invention relates to the tanning of fur skins, and moreparticularly to the tanning of such skins dehyde solutions.

Various solutions for tanning to employ the beneficial effects offormaldehyde tannage have been previously proposed, but I have found ingeneral that the tanned skins were not sufficiently soft or'that aftertanning with such mixtures such as formaldehyde and alum, on washing thesalts would be to a large extent removed and the skins would againbecome firm. The objects of this invention are to secure a tannage whichwould give a good leather which would leave the skins in a softcondition and which after washing would not become hard. I havediscovered that if the tanning solution be composed of water,formaldehyde, sodium thiosulphate and soap the desired beneficialresults can be obtained.

' In tanning by my process the dried pelts are first soaked in wateruntil soft; a small amount of an organic acid such as 0.5 percent offormic or acetic acid may be added to the soaking water to aid thesoftening. W'hen the skins have become properly softened so that themembrane is loosened and the skins themselves are plump they are workedon a fleshing machine to completely remove the membrane in order thatthe skins will take the dressing.

After flashing the skins are pickled in a salt and sulphuric acid bathconsisting, for example, of one pound of salt and one-eighth pound ofsulphuric acid per gallon of solution. The skins are Worked in thispickle until they are properly tawed, that is, until they have a drydoughy feel after which they are placed in piles to drain. The pickledskins are first soaked for a period of about one hour in a 2 percentaqueous solution of sodium thiosulp'hate and then hydroextracted in acentrifugal. They are now ready for the tanning operation proper.

The skins are now placed in a drum and milled for about two hours in asolution of sodium thiosulphate, formaldehyde and soap. I have foundthat a tanning solution consisting of 200 parts by weight of water, 5

Application filed Kay 14,

by'a process involving formal- 1981. .serial 1T0. 537,487.

parts of sodium thiosulphate, 5 parts of U. S. P. formaldehyde and 5parts of soap, will give the most satisfactory tannage. These exactpercentages may be somewhat varied without departing from the scope ofthis invention. After milling in this tannin solution the skins are hungup and allowe to dry, after which they may be finished in any desirablemanner; for example, the dry skins may be dampened back by rubbing a 10percent salt solution containing 10 percent glycerine on the flesh side;the dampened skins are then placed in piles to sammie and when uniformlydamp are milled in hardwood sawdust. The partially dried skins are againmilled in fresh clean and dry sawdust until the skins are dry andfluffy, after which the furs are freed from excess dus and finallydried.

The tanned skins may also be oiled if desired by using any good fur oilin place or" the glycerine: and salt and then treated as describedabove. Other after tanning treatments may also be applied. In thetreatment as described above, after the dust has been removed from theskins and they have been dried they may be bleached, dyed or otherwisetreated for use.

The process of this invention is applicable to any of the common furskins and I have found that it has specific value in the'tam nage ofrabbit skins or in the preparation of chamois.

Claims:

1. Method of tanning fur skins which comprises pickling the skins andsubjecting them to treatment in a tanning bath comprising water,formaldehyde, sodium thiosulphate and soap until the skins becometanned.

2. Method of tanning formaldehyde skins which comprises softening,flashing and pickling the skins, treating with a. solution of sodiumthiosulphate and then tanning in a solution of water, sodiumthiosulphate, formaldehyde and soap.

Si ned at Brooklyn in the county of Kings and tate of New York, this12th day of May,

ALLEN ROGERS.

